1. Related Field
Embodiments described herein relate generally to color adjustment for a camera.
2. Description of Related Art
Cameras are used for capturing images in different environments. Such environments include outdoors on a sunny day, outdoors on a cloudy day, indoors under incandescent (tungsten) light bulbs, and inside under florescent light bulbs. Each of these environments has a different light source: the sun, the sun filtered through clouds, and artificial lights, e.g., incandescent and florescent bulbs. Each of these light sources has a different color characteristic, e.g., a different “color spectrum” and/or a different “color temperature.” The color temperature, for example, of light is the temperature (in Kelvin) at which a heated black-body radiator matches the hue of the light.
The “color temperature” of the environment can cause captured images to have an incorrect lighting “cast.” A low color temperature shifts the lighting cast toward the red; a high color temperature shifts the lighting cast toward the blue. For example, artificial lights often may produce light of a low color temperature. Thus, images of indoor scenes illuminated by artificial light may obtain a yellow/orange cast, meaning that a white object would look yellow/orange. As another example, a clouded sun often may produce light of a high color temperature. Thus, images of scenes illuminated by a clouded sun may obtain a blue cast, meaning that a white object would look bluish.
If the camera, however, knows which object in the image is supposed to be white, the camera can calculate the difference between the measured color temperature of that object, e.g., yellow/orange, and the correct color temperature of a white object and shift all colors in the image by the same difference. This correction may be called “white balance.” If the camera can do these calculations on its own, the correction may be called “automatic white balance.”